I have a dual-boot system with Trisquel GNU/Linux and Windows 8.1, using the GRUB bootloader. However, I am having a problem where, every time I boot into Windows, it seems to be overwriting GRUB, so that on subsequent boots, it boots straight into Windows. I know how to boot into a live USB and re-install GRUB, but it is becoming a real pain to have to do it every time I boot into Windows. I need a longer-term solution to prevent Windows from overwriting my bootloader.
I am aware of this existing question at Unix & Linux SE:
However, the answers there have not helped me (and may be out of date). I have disabled Windows automatic updates and I have verified that no Windows update has been performed since last year. (I posted a follow-up on U&L SE and they recommended I try here instead).
So, does anyone know how I can absolutely prevent Windows from ever overwriting my bootloader, without my permission?
Please note that I am not looking for advice on how to re-install GRUB. I know how to do that and have done it countless times. I need a more sustainable solution to prevent Windows from screwing with my boot sector in the first place.